Heat exchangers are used in various capacities in automotive applications, e.g., radiators, heater cores, air conditioning evaporators, and condensers. Although heat exchangers vary in shape and form from one to another, generally speaking, they are made from aluminum and consist of two spaced header tanks interconnected by flow tubes having interspersed cooling fins. Fluid is circulated through the header tanks and flow tubes to effect the necessary temperature drop.
The header tanks, flow tubes, and cooling fins are rigidly attached to one another by brazing. It has been found that this brazing operation can be most efficiently accomplished in a furnace for mass production applications. The prior art teaches placing the heat exchanger workparts on a continuous belt-type flexible conveyor assembly for conveying the workparts through a brazing chamber and furnace. Because the conveyor assembly also passes through the highly elevated temperatures in the braze furnace, it also is subjected to the corrosive effects of the braze fluxes which are liquified during the early stages of the braze process.
The prior art teaches constructing the conveyor assembly from a simple, flat stainless steel mesh supported directly on top of the headers or floor in the braze furnace Although inexpensive, this process is pegged with several quality disadvantages. To overcome such disadvantages, the prior art has also taught to support the workparts on support members integral with the conveyor assembly. It is critical that these workpart support members provide a smooth and flat surface to insure that the workpart is continuously and steadily supported at all times prior to the solidification of braze alloy. If the workpart is disturbed prior to braze alloy solidification, such as what occurs when the workpart support members are unstable, uneven or jostled, then splits or cracks in the braze alloy occur resulting in faulty and unacceptable workparts.
Given this, five critical factors can be identified against which a conveyor assembly is to be evaluated. First, the conveyor assembly material must exhibit acceptable durability against corrosion in the harsh brazing environment. Second, the conveyor material in contact with the workpart must not bond to the workparts during braze solidification. Third, the conveyor assembly must provide a flat, stable surface for the workparts to ride on as the braze alloy solidifies. Fourth, the conveyor assembly must have overall good mechanical durability. And fifth, the mass of the conveyor assembly must be reduced to a minimum so that heat loading of the braze furnace will not occur.